One mechanism for hemostasis in a mammal is the formation of a blood clot. Clot formation in humans, for example, occurs by means of a complex cascade of reactions with the final steps being the conversion of fibrinogen (a monomer) in the blood by thrombin, calcium ions and activated factor XIII to ultimately form a crosslinked fibrin II polymer.
A fibrin sealant is a biological material whose effect imitates the final stages of coagulation. The prior art is replete with disclosures of two component fibrin sealant systems which co-administer fibrinogen and thrombin, typically in the presence of calcium ions and factor XIIIa, to form a fibrin clot or sealant at a desired surgical site. In prior art sealants the two sealant-forming components are co-applied or co-sprayed as liquids. The fibrinogen and thrombin interact at the surface or desired sealant site to form the fibrin polymer. Many different methods and devices have been proposed to enhance the uniformity of the mixing and interaction of the fibrinogen and thrombin components in order to enhance the uniformity of the resultant sealant. A device and method are described in WO 98/02098 which provide for a uniform mixing of the fibrinogen and thrombin components at the target surface to provide a uniform, substantially homogenous fibrin polymer sealant.
It is understood in the area of fibrin sealants that there is a xe2x80x9clagxe2x80x9d time for polymerization to commence. The thrombin needs to act upon the fibrinogen to catalyze the cleavage of fibrinopeptide A and eventually fibrinopeptide B thrombin needs to act upon the fibrinogen to catalyze the cleavage of fibrinopeptide A and eventually fibrinopeptide B from fibrinogen before the resulting fibrin can begin to polymerize. In fact, fibrinogen itself is believed to inhibit the polymerization of fibrin such that polymerization will not begin until at least 25% of the fibrinogen has been converted to fibrin I monomer, i.e., by cleavage of fibrinopeptide A. In these prior art sealants, although the efficiency of mixing and spraying may enhance the overall uniformity of the fibrin polymer formed, the characteristics of the sealant structure itself, i.e., fibril size and density, pore size and density, are primarily dependent upon concentrations of fibrinogen and/or thrombin.